Natural Product-Based Studies for the Management of Castration-Resistant Prostate Cancer: Computational to Clinical Studies

Background: With prostate cancer being the fifth-greatest cause of cancer mortality in 2020, there is a dire need to expand the available treatment options. Castration-resistant prostate cancer (CRPC) progresses despite androgen depletion therapy. The mechanisms of resistance are yet to be fully discovered. However, it is hypothesized that androgens depletion enables androgen-independent cells to proliferate and recolonize the tumor. Objectives: Natural bioactive compounds from edible plants and herbal remedies might potentially address this need. This review compiles the available cheminformatics-based studies and the translational studies regarding the use of natural products to manage CRPC. Methods: PubMed and Google Scholar searches for preclinical studies were performed, while ClinicalTrials.gov and PubMed were searched for clinical updates. Studies that were not in English and not available as full text were excluded. The period of literature covered was from 1985 to the present. Results and Conclusion: Our analysis suggested that natural compounds exert beneficial effects due to their broad-spectrum molecular disease-associated targets. In vitro and in vivo studies revealed several bioactive compounds, including rutaecarpine, berberine, curcumin, other flavonoids, pentacyclic triterpenoids, and steroid-based phytochemicals. Molecular modeling tools, including machine and deep learning, have made the analysis more comprehensive. Preclinical and clinical studies on resveratrol, soy isoflavone, lycopene, quercetin, and gossypol have further validated the translational potential of the natural products in the management of prostate cancer.

A review of the effects and molecular mechanisms of dimethylcurcumin (ASC-J9) on androgen receptor-related diseases

Dimethylcurcumin (ASC-J9) is a curcumin analogue capable of inhibiting prostate cancer cell proliferation. The mechanism is associated with the unique role of ASC-J9 in enhancing androgen receptor (AR) degradation. So far, ASC-J9 has been investigated in typical AR-associated diseases such as prostate cancer, benign prostatic hypertrophy, bladder cancer, renal diseases, liver diseases, cardiovascular diseases, cutaneous wound, spinal and bulbar muscular atrophy, ovarian cancer and melanoma, exhibiting great potentials in disease control. In this review, the effects and molecular mechanisms of ASC-J9 on various AR-associated diseases are summarized. Importantly, the effects of ASC-J9 and AR antagonists enzalutamide/bicalutamide on prostate cancer are compared in detail and crucial differences are highlighted. At last, the pharmacological effects of ASC-J9 are summarized and the future applications of ASC-J9 in AR-associated disease control are discussed.

Pharmacotherapeutic strategies for castrate-resistant prostate cancer

INTRODUCTION

Metastatic castration-resistant prostate cancer (CRPC) is a potentially symptomatic disease with an eventual lethal outcome. Novel pharmaceutical agents are continuously studied with encouraging results in CRPC.

AREAS COVERED

In this perspective, the authors present established and promising pharmacotherapeutic strategies for the management of CRPC; both with and without metastases. Apart from the different treatment strategies, the authors present the relevant sequence of treatment through disease progression.

EXPERT OPINION

Usually, docetaxel should be considered the first line treatment in mCRPC. Abiraterone acetate (AA) plus prednisone or enzalutamide (ENZ) could be alternative treatments in chemotherapy naïve patients. Sipuleucel-T has been approved for the treatment of asymptomatic or minimally symptomatic mCRPC. Ra-223 has been approved for patients with mCRPC with symptomatic bone metastases (not visceral metastases). Cabazitaxel has been approved as the second line treatment to docetaxel in mCRPC. No differences in the overall survival has been observed between sequences starting with docetaxel versus AA/ENZ. Between AA-to-ENZ and ENZ-to-AA sequence, the AA-to-ENZ sequence appeared to be more favorable than the ENZ-to-AA regarding progression-free survival but not overall survival. Carbazitaxel seemed to retain its activity regardless of the treatment sequence. Of note, ENZ and apalutamide have been approved in non-metastatic CRPC.

Correlation of Gleason Grading and Prognostic Immunohistochemistry Markers (Human Epidermal Growth Factor Receptor 2/neu and Androgen Receptor) in Prostatic Core Needle Biopsy: A Study in a Tertiary Care Center

Background: Worldwide prostate cancer is the most common cause of cancer and the second leading cause of cancer death among men. Transrectal ultrasound-guided core needle biopsies are the diagnostic modalities which help in proper categorization and grading of prostatic carcinoma, thus facilitating individualized treatment. These biopsies are the primary source for performance of additional diagnostic immunohistochemical testing for basal cell-associated markers to rule out the morphological mimicker and prognostic markers such as androgen receptor (AR) and human epidermal growth factor receptor 2 (HER2)/neu. Materials and Methods: A prospective, observational study was conducted in the department of pathology in collaboration with department of urosurgery of a tertiary care hospital. One hundred and nineteen patients diagnosed with prostatic nodules were included in this study. Values of serum prostate-specific antigen were recorded. Tissue for histopathological study was obtained in the form of core needle biopsy, and Gleason grade was calculated in all malignant cases. Immunohistochemistry for p63 and alpha-methylacyl-CoA racemase was performed as an additional test in premalignant cases. Prognostication of the prostate cancer cases was done using AR and HER2/neu. Results: A total of 119 cases aged between 20 and 90 years were included in this study. Malignant lesions reveal an increase in the percentage of AR staining in comparison to the benign glandular structure. The Gleason score with higher value (8–9) showed increased expression of HER2/neu receptor. Conclusion: Critical histopathological analysis of core needle biopsy along with immunohistochemical evaluation maximizes the diagnostic accuracy in prostate cancer cases and also helps in prognosis assessment.

Reversibility of castration resistance status after Radium-223 dichloride treatment: clinical evidence and review of the literature

In the history of prostate cancer, some of the patients progressed to castration-resistant prostate cancer (CRPC) stage and, although new drugs and treatment protocols have been introduced, CRPC presents poor prognosis. This review is focused on biological mechanisms, underlying CRPC described in scientific literature in order to explain the reversion of resistance to castration. We present the case of a 73-year-old man, affected by bone metastatic CRPC, early treated with Radium-223 with a complete response. After 15 months from Radium-223 treatment, prostate-specific antigen increased with radiological progression. Androgen deprivation therapy was again performed and was effective, despite previous CRPC condition and no known mechanisms that may explain the reversion of this condition. Therefore, to our knowledge, he is the unique described case of the reversion of resistance to castration. Nevertheless, promising aspects may be lack of intrametastatic production of androgen or the suppression of bypass androgen receptor signaling pathways. Furthermore, the cytotoxic action of Radium-223 on cancer stem cell (CSC), due to surrounding clones with high-bone turnover, or the immune response that underlying the abscopal effect, may also modulate the reversion of CRPC after Radium-223. If confirmed by multicenter trials, the reversion of CRPC may impact on the management of prostate cancer.

Molecular and cellular mechanisms of castration resistant prostate cancer

With increases in the mortality rate and number of patients with prostate cancer (PCa), PCa, particularly the advanced and metastatic disease, has been the focus of a number of studies globally. Over the past seven decades, androgen deprivation therapy has been the primary therapeutic option for patients with advanced PCa; however, the majority of patients developed a poor prognosis stage of castration resistant prostate cancer (CRPC), which eventually led to mortality. Due to CRPC being incurable, laboratory investigations and clinical studies focusing on CRPC have been conducted worldwide. Clarification of the molecular pathways that may lead to CRPC is important for discovering novel therapeutic strategies to delay or reverse the progression of disease. A sustained androgen receptor (AR) signal is still regarded as the main cause of CRPC. Increasing number of studies have proposed different potential mechanisms that cause CRPC, and this has led to the development of novel agents targeting the AR-dependent pathway or AR-independent signaling. In the present review, the major underlying mechanisms causing CRPC, including several major categories of AR-dependent mechanisms, AR bypass signaling, AR-independent mechanisms and other important hypotheses (including the functions of autophagy, PCa stem cell and microRNAs in CRPC progression), are summarized with retrospective pre-clinical or clinical trials to guide future research and therapy.

Dissecting major signaling pathways in prostate cancer development and progression: Mechanisms and novel therapeutic targets

Prostate cancer (PCa) is the most frequently diagnosed non-cutaneous malignancy and leading cause of cancer mortality in men. At the initial stages, prostate cancer is dependent upon androgens for their growth and hence effectively combated by androgen deprivation therapy (ADT). However, most patients eventually recur with an androgen deprivation-resistant phenotype, referred to as castration-resistant prostate cancer (CRPC), a more aggressive form for which there is no effective therapy presently available. The current review is an attempt to cover and establish an understanding of some major signaling pathways implicated in prostate cancer development and castration-resistance, besides addressing therapeutic strategies that targets the key signaling mechanisms.

Androgen deprivation of prostate cancer: Leading to a therapeutic dead end

Androgen deprivation therapy (ADT) is considered as the standard therapy for men with de novo or recurrent metastatic prostate cancer. ADT commonly leads to initial biochemical and clinical responses. However, several months after the beginning of treatment, tumors become castration-resistant and virtually all patients show disease progression. At this stage, tumors are no longer curable and cancer treatment options are only palliative. In this review, we describe molecular alterations in tumor cells during ADT, which lead to deregulation of different signaling pathways and castration-resistance, and how they might interfere with the clinical outcome of different second-line therapeutics. A recent breakthrough finding that early chemotherapy is associated with a significant survival benefit in metastatic hormone-sensitive disease highlights the fact that there is time for a fundamental paradigm shift in the treatment of advanced prostate cancer. Therapeutic intervention seems to be indicated before a castration-resistant stage is reached to improve therapeutic outcome and to reduce undesirable side effects.

Genetic variation: effect on prostate cancer

The crucial role of androgens in the development of prostate cancer is well established. The aim of this review is to examine the role of constitutional (germline) and tumor-specific (somatic) polymorphisms within important regulatory genes of prostate cancer. These include genes encoding enzymes of the androgen biosynthetic pathway, the androgen receptor gene, genes that encode proteins of the signal transduction pathways that may have a role in disease progression and survival, and genes involved in prostate cancer angiogenesis. Characterization of deregulated pathways critical to cancer cell growth have lead to the development of new treatments, including the CYP17 inhibitor abiraterone and clinical trials using novel drugs that are ongoing or recently completed [1]. The pharmacogenetics of the drugs used to treat prostate cancer will also be addressed. This review will define how germline polymorphisms are known affect a multitude of pathways, and therefore phenotypes, in prostate cancer etiology, progression, and treatment.

Overexpression of HER-2/neu in patients with prostatic adenocarcinoma

BACKGROUND

Prostatic adenocarcinoma is one of the main causes of cancer death, and its timely diagnosis and preventing its progression dramatically helps improve life indexes. Given the high disease recurrence rate, today, research is more inclined toward exploring causes of recurrence and development, and innovation of modern treatment methods. Several studies have explored over-expression of human epidermal growth factor receptor 2 (HER-2/neu) in prostatic cancer so far, with different results. Thus, it was decided to investigate HER-2/neu overexpression in patients with prostatic adenocarcinoma in Iran.

MATERIALS AND METHODS

A sample size of 40 patients with prostate cancer entered the study, using a cross-sectional, non-randomized sampling method. Parameters studied included patient age at surgery, Gleason score, serum prostatic specific antigen (PSA) before surgery, and positive sample rate after immunohistochemical staining to investigate HER-2/neu overexpression.

RESULTS

In terms of HER-2/neu receptor staining rate, of 40 slides, 16 (40%) scored 0, 13 (32.5%) 1+, 7 (17.5%) 2+, and 4 (10%) 3+. In total 27.5% of slides showed HER-2/neu overexpression. In terms of age, an inverse correlation was found (-0.181), but without significance (p=0.263). In terms of serum PSA, the correlation coefficient was 0.449 (p=0.004). With respect to Gleason score, the coefficient was 0.190 (p=0.240).

CONCLUSIONS

In this study, HER-2/neu overexpression occurred in 27.5% of prostate cancer cases, which is a relatively high figure, compared to similar studies elsewhere. While, we failed to reveal any relationship between HER-2/neu expression status with progression and prognosis of disease, it was demonstrated that the serum PSA level was significantly higher in cases with increased receptor expression.

[Prostate cancer: promising biomarkers related to aggressive disease]

BACKGROUND

Although a rapidly growing number of candidate biological markers of prognosis and/or response to specific treatments in prostate cancer, none have to date showed ability to completely prognosticate prostate cancer on evidence based urology.

OBJECTIVE

To review the pertinent literature on the issue.

ACQUISITION OF EVIDENCE

A comprehensive review of the current literature was done focusing on promising biomarkers related to aggressive prostate cancer.

SUMMARY OF EVIDENCE

Combined with the heterogeneous nature of the disease, mixed case series are the most common study design, impeding robust results and the development of an effective therapeutic strategy. Improvement in prostate cancer patient survival requires not only the identification of new therapeutic target based on detailed understanding of the biological mechanisms involved in metastatic dissemination and tumor growth but strong clinical studies as well.

CONCLUSION

Better study design involving potential markers and including well-classified and staged patients with robust methodology and adequate outcomes (mainly survival) are necessary to the field evolution.

Phage displayed peptides/antibodies recognizing growth factors and their tyrosine kinase receptors as tools for anti-cancer therapeutics

The basic idea of displaying peptides on a phage, introduced by George P. Smith in 1985, was greatly developed and improved by McCafferty and colleagues at the MRC Laboratory of Molecular Biology and, later, by Barbas and colleagues at the Scripps Research Institute. Their approach was dedicated to building a system for the production of antibodies, similar to a naïve B cell repertoire, in order to by-pass the standard hybridoma technology that requires animal immunization. Both groups merged the phage display technology with an antibody library to obtain a huge number of phage variants, each of them carrying a specific antibody ready to bind its target molecule, allowing, later on, rare phage (one in a million) to be isolated by affinity chromatography. Here, we will briefly review the basis of the technology and the therapeutic application of phage-derived bioactive molecules when addressed against key players in tumor development and progression: growth factors and their tyrosine kinase receptors.

Effects of ARHI on cell cycle progression and apoptosis levels of breast cancer cells

The purposes of this study were to investigate the role of Aplysia Ras Homolog I (ARHI) on cell growth, proliferation, apoptosis, and other biological characteristics of HER2-positive breast cancer cells. Our goal was to provide experimental evidence for the development of future effective treatments of HER2-positive breast cancer. A pcDNA3.1-ARHI eukaryotic expression vector was constructed and transfected into the human HER2-positive breast cancer cell lines SK-BR-3 and JIMT-1. Then, various experimental methods were utilized to analyze the biological characteristics of ARHI-expressing breast cancer cells and to examine the impact of expression of the ARHI gene on cyclin D1, p27(Kip1), and calpain1 expression. We further analyzed the cells in each group after treatment with trastuzumab to examine the effects of this drug on various cellular characteristics. When we compared pcDNA3.1-ARHI-expressing SK-BR-3 and JIMT-1 cells to their respective empty vector and control groups, we found that cell viability was significantly lower (p < 0.05) in the ARHI-expressing cells, and the proportions of G1 phase cells and apoptotic cells were significantly higher in the ARHI-expressing cells (p < 0.05). In all groups of SK-BR-3 cells, trastuzumab treatment significantly decreased cell growth (p < 0.05). The proportion of cells in G1 phase and the number of apoptotic cells in the pcDNA3.1-ARHI-expressing group were significantly higher than that in the empty vector group and the control group (p < 0.05). The growth of pcDNA3.1-ARHI-transfected JIMT-1 cells was significantly decreased (p < 0.05), while the proportion of apoptotic cells was significantly increased (p < 0.05). Cell growth, viability, and the percentage of apoptotic cells were similar between the JIMT-1 empty vector and control groups. ARHI expression inhibited cyclin D1 expression in SK-BR-3 cells and JIMT-1 cells, while it promoted p27(Kip1) and calpain1 expression in these cells. ARHI expression inhibits the growth and proliferation of HER2-positive breast cancer cells, while it also promotes apoptosis in these cells. ARHI expression also improves the sensitivity of JIMT-1 cells to trastuzumab by inducing apoptosis.

Molecular markers that can be utilized in diet and dietary supplement research

Prostate and other cancers have a multitude of potential markers that can be used in laboratory and clinical studies of diet and dietary supplement interventions. More overt clinical markers include imaging tests, biopsy samples, prostate-specific antigen kinetics, and urinary testing. Many molecular markers are currently available, including antiapoptotic and apoptotic proteins, cell adhesion molecules, cell cycle compounds, growth factors, angiogenic markers, and proliferative and inflammatory signals. Protein kinases and transcription factors should also be considered for diversity. Testing of numerous molecular markers has become critical in gaining preliminary insight into the potential impact of a novel diet and supplemental agents.